Composer不会安装依赖项

I have tried to install some dependencies that I need, for instance, PHPUnit and Slim, onto my project directory (not globally).

I have this in my composer.json,

{
    "require-dev": {
        "phpunit/phpunit": "*"
    }
}

This is my directory structure,

controller/
tests/
composer.json

When I run this line composer update on my Windows CMD, I get this message below on the CMD and it's just frozen there and doing nothing else. No PHPUnit is intall to my vendor directory at all.

enter image description here

any ideas what have I missed?

EDIT:

ping,

enter image description here

EDIT 2:

autoloading,

{
    "autoload": {
        "psr-4": {
            "Vendor\\Namespace\\": ""
        }
    }
}